Showing papers on "Aphid published in 1976"

Aphid Parasites (Hymenoptera Aphidiidae) of the Mediterranean Area

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Ant-aphid association: role of aphid alarm pheromone.

Abstract: When attacked by predators, aphids secrete alarm pheromones that cause nearby aphids to disperse. Ant-associated (myrmecophilous) aphid species disperse less readily than nonmyrmecophilous species. The ant Formica subsericea responds to aphid alarm pheromone in a way that is beneficial to the aphid. These findings support our hypothesis that myrmecophilous aphids depend more on ants for protection from predators than on their own dispersive powers.

Influence of crop background on natural enemies of aphids on Brussels sprouts

Abstract: SUMMARY The most abundant natural enemies of aphids on Brussels sprout crops were Syrphidae, different species being attracted differentially to weedy or weed-free plots according to whether they were more host-plant-orientated (e.g. Melanostoma spp., Platycheirus spp.) and thus affected directly by the background, or more aphid-orientated (e.g. Syrphus balteatus) and so less affected by background than by aphid numbers. Oviposition by Melanostoma spp. was usually much greater in weedy sprout crops than on sprouts in bare soil, and their eggs were also very abundant on weeds. Eggs of other syrphid species were scarcer on weeds. In contrast to Melanostoma, Platycheirus spp. usually oviposted preferentially on sprouts growing in bare soil. Oviposition by S. balteatus was in response to aphid abundance and thus tended to become greater on sprouts in bare soil. Notably more adults of non-aphido-phagous Syrphidae were caught over weedy than over non-weedy Brussels sprout plants. Anthocoris nemorum nymphs and adults were very common on sprout plants and weeds in the weedy crop but were scarce on sprouts in bare soil; A. nemorum oviposited on white and yellow charlock (Raphanus raphanistrum and Sinapis arvensis) occasionally. Parasitism of Brevicoryne brassicae by Diaeretiella rapae appeared to be related to aphid numbers and was only indirectly influenced by the crop background. Field experiments with green and brown cloth backgrounds showed that some syrphids were attracted to green; A. nemorum was relatively scarce over both artificial backgrounds. It is concluded that decreased natural enemy action is partly responsible for the initially greater abundance of B. brassicae in a weed-free crop of Brussels sprouts than in a weedy crop.

Reproductive strategies of the alate morphs of the bird cherry-oat aphid rhopalosiphum padi l.

Abstract: Host alternating aphids like the bird cherry-oat aphid exist in several distinct morphs (Dixon 1973). The alate morphs are difficult to separate morphologically (Rogerson 1948) but are easily separated behaviourally. The emigrants leave the primary host, bird cherry, Prunus padus L., before the end of June and colonize various grasses. The alate exules, which are then produced on the secondary hosts, spread to other grass plants. Triggered by fall in temperature and decrease in day-length in autumn, exules no longer produce more exules, but gynoparae and males instead, which finally return to the primary host on which the aphid overwinters as an egg (Dixon & Glen 1971). Each morph in the sequence that is produced in the annual cycle of a host alternating aphid has a different function to perform. Associated with their different functional roles it is acceptable that these morphs also exhibit different reproductive strategies. It is the aim of this paper to describe these differences in the reproductive behaviour of all the alate female morphs of Rhopalosiphum padi L. and to relate the differences to the aphid's way of life.

Effects of temperature on overwintering populations of the green spruce aphid Elatobium abietinum

Abstract: SUMMARY Recorded minimum temperatures of – 7 oC or lower noticeably reduced overwintering populations of the green spruce aphid, Elatobium abietinum, in north-east Scotland. It is suggested that, at these temperatures, ice formation in the needles of the host Sitka spruce, caused attached aphids to freeze. Aphid mortality also occurred when maximum temperatures did not rise above + 6 oC for prolonged periods, possibly as a result of starvation following an extended chill coma. A diagrammatic representation of the main factors affecting anholocyclic populations of E. abietinum during the winter is presented to emphasize the governing role played by temperature. The balance between mortality and recruitment determines the size of the population at the end of the winter, and this in turn determines the subsequent summer infestation. It should be possible, therefore, to predict aphid outbreaks either from winter temperatures or from the number of aphids present at the end of the winter. Temperature records obtained from integrating thermometers indicated that the inside of the lower crown tended to be the warmest part of the tree during the winter, resulting in greater aphid survival in the lower branches.

The role of the helper virus, anthriscus yellows, in the transmission of parsnip yellow fleck virus by the aphid Cavariella aegopodii

Abstract: SUMMARY Transmission of parsnip yellow fleck virus (PYFV) by the aphid Cavariella aegopodii occurs only when the aphids are also carrying the helper virus, anthriscus yellows (AYV). None of five other viruses tested was able to act as helper. In experiments in which aphids were allowed to feed through membranes on crude or treated extracts from infected plants, aphids already carrying AYV acquired PYFV, but virus-free aphids failed to acquire either AYV or PYFV. PYFV was not transmitted by insects injected with haemolymph from aphids carrying both viruses, or with purified preparations of PYFV. PYFV was transmitted when AYV-carrying aphids, except those whose stylets had been removed, were contaminated externally with PYFV preparations. Ultraviolet irradiation of infected leaves did not prevent aphids from acquiring AYV, presumably because it is confined to deeply-lying tissues. AYV-carrying aphids could acquire PYFV from u.v.-irradiated leaves after acquisition access times of 2 h but not after feeds of only 2 or 15 min (which are adequate on unirradiated leaves), suggesting that PYFV is present in all parts of the leaf. No ‘helper agent’ distinct from AYV itself was detected in these experiments or in experiments on minimum acquisition feeding time or maximum period of persistence in the aphid. U.v.-inactivated PYFV competed with infective PYFV for retention sites in AYV-carrying aphids, whereas AYV apparently did not. It is suggested that there is no helper agent for PYFV, other than AYV particles. The possibility that there is one for AYV is not excluded.

Effect of Artificial Honeydews on Insect Communities in Potato Fields

Abstract: During 1972 and 1973, a field study consisting of 5 experiments was conducted to determine the effect of artificial honeydews on insect communities in potato fields. Treatments were based on either yeast hydrolysate or Feed-Wheast® (produced by culturing the yeast, Kluyveromyces fragilis Jorgensen, on cottage cheese whey) combined with honey and molasses. Feed-Wheast® was also used with tryptophan. Freshly extracted aphid juice was used alone and combined with Feed-Wheast® to test its effect on oviposition of syrphid flies. Treatments of artificial honeydews significantly increased the numbers of predatory insects: Chrysopa carnea Stephens, Hippodamia spp., Coccinella transversoguttata richardsoni Brown, Sphaerophoria cylindrica (Say), and Syrphus sp. Fecundity of C. carnea was significantly increased by the treatments. Two predators, Nabis alternatus (Parsh.) and Orius tristicolor White were reduced in treated plots. Neither artificial honeydews nor aphid juice treatments stimulated syrphid flies to lay eggs on sprayed plants. Numbers of Myzus persicae (Sulzer), Lygus hesperus Knight, Leptinotarsa decemlineata (Say) and Autographa californica (Speyer) were significantly reduced in treated areas.

Searching by Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and escape behaviour of its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne)

Abstract: 1 The paper describes the behavioural interactions between searching larvae of Adalia bipunctata and its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne). 2 The frequency with which the predator achieves contact with cicadellid nymphs of differing ages is related to direction of predator approach and predator perception by the cicadellid. 3 The success of a coccinellid in contacting and capturing its aphid prey is related to the predator's size and direction of approach, the perception of the predator by an aphid and the latter's ability to escape, the effectiveness of which is discussed.

Feeding and Nutrition of the Pea Aphid, Acyrthosiphon Pisum (Harris), with Special Reference to Amino Acids

Abstract: A brief review is given of the nutritional investigations made over the past twenty years on the pea aphid, Acyrthosiphon pisum, including the development of a chemically defined diet with a suitable amino acid mixture. The effects of total amino acid concentration on diet and amino acid uptake and growth of A. pisum, as well as the influence of individual amino compounds on phagostimulation are discussed. Correlations are drawn between results on diets and those obtained on pea plants. The concentrations of total soluble amino compounds (some 21 to 24 amino acids and amides), including those of 10 amino acids essential to pea aphid, and of two amides (asparagine and glutamine) are generally twice as high in water extracts of susceptible pea varieties than in those of resistant ones, and two to four times higher in terminal growth (susceptible) than in middle growth (resistant) samples of pea plants. Aphid sap uptake is also higher on susceptible than on resistant varieties. The conclusion remains that, under natural conditions, the establishment of aphid colonies of economic importance on cultivated plants is influenced markedly, among other things, by the nutritional superiority of the host, in which free amino compounds play an important part.

The effect of leaf excision on the performance of Myzus persicae and Brevicoryne brassicae in relation to the nutrient treatment of the plants

Abstract: Two groups of brussels sprout plants of one variety given different fertilizer treatments proved ‘resistant’ and ‘susceptible’ to both Myzus persicae and Breicoryrie brassicae, as measured by aphid mean relative growth rate. The hypothesis that leaf disc would fail to reflect differences in ‘nutritionallybased’ plant resistance was confirmed with B.brussicue but not M.persicae. Both aphids grew more slowly on discs than leaves of ‘susceptible’ plants; the reverse tendency showed on ‘resistant’ material. Total:(, amino nitrogen proved poorly correlated with aphid performance. Previously published (van Emden & Bashford, 1971) equations relating individual amino acids to aphid performance gave a better fit to the results, but still failed to account for the reduced performance of the aphids on ‘susceptible’ discs.

Attraction of insects to potato plants through use of artificial honeydews and aphid juice

Abstract: Three field experiments were conducted to determine the attractiveness of artificial honeydews and aphid juice to insects. Honeydew mixtures were composed of molasses, honey and tryptophane alone or combined with Feed-Wheast®, (produced by culturing the yeastKluyveromyces fragilisJorgensen on cottage cheese whey). Potato plants,Solanum tuberosum L., treated with sprays of these mixtures attracted the following predatory insects: green lacewings,Chrysopa carneaStephens; ladybird beetlesHippodamia spp.,Coccinella transversoguttataBrown,Scymnus postpinctusCasey; andGeocoris pallensStal.Lygus hesperusKnight, a phytophagous species was also attracted. Honey and tryptophane were the most attractive to all species. Aphid juice was attractive to several predators but not to lygus bugs. Orientation through olfactory response was indicated for ladybird beetles and lygus bugs. The predatory species attracted are important in the natural control of potato insects. The attraction ofL. hesperus to artificial honeydews may be useful in the control of this pest.

Factors determining the distribution of sycamore aphids on sycamore leaves during summer

Abstract: 1 In summer the sycamore aphid's responses to gravity, light direction and intensity and unidentified features of a leaf's surface result in the aphid settling and feeding on the undersurface of leaves. 2 At this time the petioles are a poor source of food and are not colonized. 3 Removal of leaf laminae results in premature abscission of the petioles. Prior to abscission the petioles become senescent and a richer food source than the laminae of mature leaves, and are colonized by aphids.

Control of the Green Peach Aphid and Its Effect on the Incidence of Potato Leaf Roll Virus

Abstract: Although several insecticides provided excellent control of Myzus persicae (Sulzer), none prevented the occurrence of potato leaf roll virus (PLRV) infection duro ing 4 yr of experimentation. There appeared to be no correlation between populations of apterous aphids in treated plots during a given year and the occurrence of PLRV infection in tubers from the plots. The overall incidence of PLRV infection was highest in years of the greatest aphid populations but appeared to be correlated with the numbers of winged aphids as indicated by catches in Moericke traps.

Aphids and Other Insects as Vectors of Soybean Mosaic Virus

Abstract: Field observations of soybean mosaic (SMV) gave evidence that a vector was responsible for spread from soybean plant to soybean plant. Ten species of insects commonly found on soybeans did not transmit SMV to healthy Bansei soybean plants. Aphids were not commonly found on soybeans but were occasionally observed probing on them. Seven aphid species colonizing weeds within the soybean fields were tested for their potential to transmit SMV. Dactynotus ambrosiae (Thomas), Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Rhopalosiphum maidis (Fitch) positively transmitted SMV from SMV infected soybeans to healthy soybeans. R. maidis and D. ambrosiae have not previously been reported as vectors of SMV.

A Preliminary Study of Host Selection and Acceptance Behaviour in the Cabbage Aphid,Brevicoryne BrassicaeL

Abstract: The present study investigates the role of the chemical senses in host selection and acceptance behaviour of the cabbage aphid Brevicoryne brassicae L. In order to determine the composition of this behaviour we observed aphids on hosts, non hosts and intermediate plants on which the aphid incidentally occurs (Markkula, 1953): non-cruciferous plants which contain mustard oil glucosides. About fifteen different behavioural components were distinguished and scored during a period of 30 minutes after an aphid had benn put on a plant. On formal grounds we used 1he term “proboscis contact” (p.c.) instead of “probe”. Some authors (cf. Klingauf, 1971) use the duration of the first walk or the first probe as parameters in host selection behaviour. In our experiments the frequency of p.c., its mean duration and the percentage of time spent in p.c. were used. These parameters appeared to be less sensitive to pretreatments and reflected greater differences between the various plant species than the duration of the first walk or first probe. Apterous adults showed (Fig. 1) on the host Brussica oleracea a relatively low frequency of p.c. compared to aphids on the non host Vicia faba. The mean duration of p.c. and the percentage of time spent in p.c. were relatively high on host-plants. Compared with Brassica, Tropaeolum majus was, under our experimental conditions, an equally attractive host for aphids. Similar results were found with alate insects (Fig. 2). Aphid behaviour on Reseda odorata may be described as intermediate as compared to Brassica and Vicia.

Chromosome numbers of parthenogenetic females of fifty-five species of Aphididae (Homoptera) new to cytology

Abstract: The numbers of somatic chromosomes of 55 species of Aphididae are presented. Squashed embryos from apterous viviparous females are stained with crystalviolet. Some relationships between aphid chromosomes and aphid systematics are discussed.

The population dynamics of the stinging nettle aphid, Microlophium carnosum (Bukt.)

Abstract: 1 Populations of Microlophium carnosum on patches of perennial stinging nettle, Urtica dioica increased rapidly during April and May to reach their peaks in June. The decline in numbers was equally rapid and very small populations persisted into autumn; parthenogenetic over-wintering was recorded. 2 Suboptimal ambient temperature and mortality due to natural enemies contributed mainly to the post-peak development of aphid populations. 3 The combined effects of intraspecific competition and a deterioration in the food quality of the host plant appeared to be the major factors determining the temporal pattern of aphid abundance. 4 Variation in the size of populations between the three sampled sites was correlated with differences in the food quality of nettles as indicated by aphid mean relative growth rate. 5 Each nettle patch has a particular ‘carrying capacity’ for aphids, within which a biennial fluctuation between relatively large and small aphid populations appeared to be emerging at most of the sites investigated. A natural or aphid-induced cycle in host plant quality, or alternatively, the persistent effects of intraspecific competition over several generations, may explain this fluctuation.

Bionomics of Aphis gossypii on Resistant and Susceptible Cantaloupe

Abstract: Bionomics of the melon aphid, Aphis gossypii Glover, were studied on resistant and susceptible cantaloupe, Cucumis melo L., plants. In the field, there was no difference between the age distributions of populations on resistant and susceptible plants. However, late in the season, a significantly greater proportion of the population on susceptible plants consisted of alatoid nymphs. Alate adults confined to resistant plants in the greenhouse suffered significantly greater mortality and produced only ca. 25% as many progeny as their counterparts on susceptible plants. Apterous aphids on resistant plants were smaller, had a significantly longer prereproductive period, and significantly shorter reproductive and postreproductive periods than those on susceptible plants. Approximately equal percentages of aphids on resistant and susceptible plants produced offspring, but the x ¯ fecundity on the former was only ca. ⅓ that on the latter. This was attributable to both a lower reproductive rate among reproducing aphids and a higher mortality rate during the reproductive period on resistant than on susceptible plants. Populations of A. gossypii were maintained for up to 5 generations on resistant plants, with no danger of extinction.

Selected Predators of Aphids in Grain Sorghum and Their Relation to Cotton

Abstract: There was a seasonal relationship in abundance of greenbug, Schizaphis graminum (Rondani), and corn leaf aphid, Rhopalosiphum maidis (Fitch), and several selected predators on field planted sorghum, wheat, and volunteer johnsongrass. As aphid numbers increased on any host, predators also increased. As parasitism decreased aphid population levels in grain sorghum, predator density decreased in that crop. Predator population levels in cotton began to increase at about the same time that predator density began to decrease in sorghum. Based on the relative similarity of the 2 habitats in terms of species composition, the 2 different plant communities became more intimately related as the growing season progressed. Of ca. 500,000 predators captured, marked and released in grain sorghum, 51 or 0.01% were recaptured in nearby cotton.

Area control of the green peach aphid on peach and the reduction of potato leaf roll virus

Abstract: Peach trees in a 500-mile2 (1295 sq. K) area were sprayed during April and May each year from 1966 to 1969 to control the wingless fundatrix form ofMyzus persicae (Sulzer) after the overwintering eggs had hatched and before subsequent generations of the aphids had developed wings and migrated to summer host plants. The results were monitored from 1966 to 1971 by using about 60 yellow water trap pans each year to collect winged aphids in the control area. Also, aphids were counted weekly in about 30 potato fields each year. Samples of potato tubers collected from the 30 fields (and from 34 other fields in 1965) were indexed for net necrosis and then planted and indexed for chronic leaf roll.

Breeding behavior of resistance to green peach aphid in tuber-bearing Solanum germplasm

Abstract: Fifty-seven tuber-bearingSolanum progenies including species and interspecific hybrid derivatives were evaluated for resistance to green peach aphid (GPA),Myzus persicae (Sulzer), using an excised leaflet test. The progenies segregated for resistance and most contained some highly resistant clones. Resistance appeared to be partially dominant and genotype-environment interaction was low. Heritability estimates of 50–60 percent were obtained from both diploid and tetraploid populations.

Aphid behaviour and host-plant preference demonstrated by electronic patterns of probing and feeding

Abstract: The electronic traces resulting from the interaction of aphid salivation and plant fluid ingestion from acceptable and non-acceptable food sources are shown for the four potato-infesting aphid species,Myzus persicae (Sulzer),Macrosiphum euphorbiae (Thomas),Aphis nasturtii Kaltenbach, andAulacorthum solani (Kaltenbach). The behaviour of the four species on the aphid susceptible potato variety Katahdin, is described as a standard and the range of salivation intervals is used to describe the initial feeding behaviour of the aphid on its food source. The different periods spent in salivation prior to ingestion are further described and used to develop five categories of host acceptability, ranging from very acceptable (V), to unacceptable (I), based on the frequency of interruptions (aborts). This provides a means of screening potato materials for their resistance to aphid exploitation. It is shown that host discrimination occurs very early in the feeding approach.

Influence of Cultivars and Pesticides on Pea Aphid, Spotted Alfalfa Aphid, and Associated Arthropod Taxa in a Minnesota Alfalfa Ecosystem

Abstract: Influence of cultivars and pesticides on population trends and interrelationships of pea aphid, Acyrthosiphon pisum (Harris), spotted alfalfa aphid, Therioaphis maculata (Buckton), and associated arthropod taxa were studied over 3 growing seasons at Rose-mount, Minn. Greatest cultivar differences in resistance were for pea aphid and spotted alfalfa aphid. Cultivar differences were less for other pest species, but significant some sampling periods. Pesticides increased forage yields, the benefit varying with severity of pest pressure and cultivar. Fungicidal sprays resulted in greater yield increases than did insecticidal sprays; combinations were additive in effect. Populations of both aphid species and of associated entomophagous taxa were consistently higher in subplots treated with fungicides. Fungicidal sprays enhanced aphid populations by suppressing entomogenous fungi. Weekly correlations between populations of aphids and associated arthropod taxa revealed consistent patterns of significant positive correlation. Taxa tending to strong association with pea aphid included: tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); alfalfa plant bug, Adelphocoris lineolatus (Goeze); the coccinellids, Hippodamia convergens Guerin-Meneville, H. tredecimpunctata tibialis (Say), and Coleomegilla maculata lengi Timberlake; Orius insidiosus (Say); Chrysopa spp.; hemerobiids; syrphids; spiders; nabids; and parasitic wasps. Taxa tending to strong association with spotted alfalfa aphid included potato leafhopper, Empoasca fabae (Harris); hemerobiids; nabids; Orius insidiosus ; spiders; and parasitic wasps. Strong positive correlations between either aphid species and any entomophagous taxon were interpreted as evidence of a density-dependent relationship.

Comparison of Aphids Trapped on Vertical Sticky Board and Cylindrical Aphid Traps and Correlation with Watermelon Mosaic Virus 2 Incidence

Abstract: Sticky board aphid traps of 1290 cm2 and sticky cylindrical traps of 1225 cm2 were equally suitable for quantitative studies of aphid vectors of watermelon mosaic virus 2 (WMV-2). There were no differences between traps in total numbers of aphids or numbers of species caught or in numbers of Aphis spiraecola Patch, the main vector. At peak aphid migration, A. spiraecola comprised 81% of the catch on both traps. Correlations of trapped aphids with mosaic incidence the same week and one week later were both significant, but the correlation of trapped aphids with mosaic incidence 2 wk later was much better. Traps located south and east of a 7.3 ha watermelon field were closer to the area of highest mosaic incidence than north and west traps, but correlations of aphids trapped on boards or cylinders with mosaic incidence were highly significant regardless of trap location.